You can go real tight on a naturally aspirated car, as long as the valves close hot and cold, you just can't go too loose. Diesels and turbos working for living you need to make sure you give the valve a little time to cool, but that is as much a function of duration of the lobe as it is lash
For example, I run my Erson in the Mustang at .014 they spec it for .028, the Bullet in my truck, I ran at .016, and they spec'd it at .026.
The Poncho was a unique one, knew very little about the internals and by the time I picked the lobes, it could have been just as easy to buy a 280H and retard it a little.
Regardless, the car has real resto pea shooter exhaust, but we replaced a bad cam, one lobe was bad, but it also was a crappy Crane with a wide LSA and no duration. The car is night and day difference, he is on a "3 young kids" budget, so next step is 3 inch mandrel bent with an H or X, and the next after that is a Performer RPM. Both should likely make a noticeable difference